1. Field of the Invention
The present invention relates to sealing assemblies of a valve, and more particularly, to vacuum valve having double seal plates and capable of solidly sealing.
2. Description of the Related Art
As disclosed in FIGS. 19˜21 of U.S. Pat. No. 7,090,192, a vacuum valve comprises a valve body internally provided with a gate assembly rotatably driven by a swing arm, wherein the gate assembly is allowed to open or close against a valve opening of the valve body. Therein, the gate assembly has two gate plates, one steel ball plate between the two gate plates, and a plurality of rolling steel balls on the steel ball plate. Also, the inner side of the gate plate is provided with a plurality of driving grooves corresponding to the rolling steel balls, while the depth of the driving grooves varies from being deep to shallow. When the gate assembly seals the valve opening, the steel ball plate is further driven, such that the rolling steel balls move from the deep position to the shallow position of the driving grooves. As a result, the two gate plates are pushed outward, separately, such that the gate plates rigidly contact the valve opening to achieve a highly seal air-tight status.
However, the contact relationship between the rolling steel balls, the gate plates, and the driving grooves is a point-contact relationship. A counter force produced during the two gate plates being pushed outward concentrates on the contact points, so that the bearable pressure per unit square measure of the rolling steel balls is limited, so as to limit the contact force between the gate plates and the valve opening. Furthermore, due to the long period usage, the rolling steel balls are easily worn down and broken, causing the demand of maintenance. As a result, the valve body of such a vacuum valve needs to be dismantled, and all the components thereof shall be taken out for facilitating the maintenance of the components such as rolling steel balls, failing to meet the requirement of being conveniently applied.